1. Field of the Invention
The present invention relates to negative-tone photoresist compositions used in extremely fine processing of a semiconductor device using extreme ultraviolet light (EUV light), materials for forming patterns used in the negative-tone resist compositions, and a method of patterns on a semiconductor device fabricated by using the negative-tone photoresist compositions.
2. Descriptions of the Related Arts
Nanofabrication by lithography using a photoresist is performed in a semiconductor device manufacturing process. In association with the recent tendency for a higher degree of circuit integration, fine patterns with the size less than 100 nanometers are often formed. A wavelength of beams or rays used for exposure has been increasingly reduced from that of a KrF excimer later beam (with the wavelength of 248 nm) to that of an ArF excimer laser beam (with the wavelength of 193 nm), and now the combination of the immersion exposure technique with ArF enables fabrication at the level of 100 nanometers or below. To realize nanofabrication at the level of 50 nanometers or below, the lithography technique using the extreme-ultraviolet rays (EUV light with the wavelength of 13.5 nm) or an electron beam is now under development. Now it is required to form various fine patterns including a hole pattern, an isolated line pattern, or a line-and-space, and therefore both positive-tone and negative-tone resist materials are required.
Another important factor which is important like the dimensions is processing accuracy, and it has been found that line edge roughness causes non-uniformity in pattern dimensions gives influences to performance of semiconductors.
To perform lithography, it is necessary to use a resist material based on a novolak resin or an acryl-based resin having the molecular weight of several thousands to several tens of thousands.
As the negative-tone resist material, the negative-tone resist for ArF described in JP-A-2003-195502 (Patent document 1) is well known. This resist has a hydrophilic γ-hydroxycarboxylic acid structure in a macromolecule side chain of the acrylic structure. In the exposed portion, intramolecular esterification occurs in the γ-hydroxycarboxylic acid moiety due to an effect of an acid generated from an acid generator, and the hydrophilic characteristic is changed to the hydrophobic one. Therefore, after development using an alkaline developer, the exposed portion becomes insoluble, and a negative-tone pattern is generated.
On the other hand, recently there are also research activities aiming at forming finer patterns not using macromolecules with the size of several nanometers or more, but using resist based on low-molecular-weight compounds with the size of 1 to 2 nanometers. A cross-linking type negative-tone resist using calixarene is reported in Journal of Photopolymer Science and Technology, 2000, 13, p. 413 (Non-patent document 1) and Japanese Journal of Applied Physics, 2005, 44, 7B, p. 5581 (Non-patent document 2. WO 2004/012012 Publication (Patent document 2) describes resist containing a non-polymer molecule as a main ingredient, and the molecule can provide high resolution and low LER, and has four or more reactive sites which are reactive moieties for the polarity-change reaction.
In the lithography process using a resist, it is required to improve the sensitivity from the view point of productivity.